Untitled

<html>
<body>
<?php
if ($_POST)
{
	require_once 'db.php';

	$username = mysql_real_escape_string(preg_replace('/[a-zA-Z0-9]/', '', $_POST['username'])); // Only allows alphanumeric characters for username
	$password = $_POST['password'];
	$confirm = $_POST['confirm'];
	if ($_POST['username'] !== $username) // Check username input
	{

		echo 'Your username must only contains alphanumeric characters';

	}
	elseif ($password !== $confirm) // Check password confirmation
	{

		echo 'Your password do not match';

	}
	else
	{

		$result = mysql_query('SELECT COUNT(id) AS found FROM users WHERE username = "'.$username.'"');
		if($result) // Username taken
		{

			echo 'Username is already taken';

		}
		else
		{

			$password .= '46jhdgj$^&#$^+_DF';
			$password = mysql_real_escape_string(sha1(strrev($password)));
			mysql_query('INSERT INTO users (id, username, password) VALUES ("", "'.$username.'", "'.$password.'")'); // Insert the registration data to the database... (id, username, password)

			echo 'Successfully registered!';

		}
	}

}
?>
<form name='register' method='post' action='register.php'>
	Username: <input type='text' name='username' /><br />
	Password: <input type='text' name='password' /><br />
	Confirm: <input type='text' name='confirm' /><br />
	<input type='submit' value='Submit' />
</form>

</body>
</html>